[show abstract][hide abstract] ABSTRACT: We use the R-matrix theory to fit low-energy data on nuclear reactions involved in Big Bang nucleosynthesis. Special attention is paid to the rate uncertainties which are evaluated on statistical grounds. We provide S factors and reaction rates in tabular and graphical formats.
[show abstract][hide abstract] ABSTRACT: From the observations of the anisotropies of the Cosmic Microwave Background (CMB) radiation, the WMAP satellite has provided a determination of the baryonic density of the Universe, \Omega_b.h^2, with an unprecedented precision. This imposes a careful reanalysis of the standard Big-Bang Nucleosynthesis (SBBN) calculations. We have updated our previous calculations using thermonuclear reaction rates provided by a new analysis of experimental nuclear data constrained by $R$-matrix theory. Combining these BBN results with the \Omega_b.h^2 value from WMAP, we deduce the light element (4He, D, 3He and 7Li) primordial abundances and compare them with spectroscopic observations. There is a very good agreement with deuterium observed in cosmological clouds, which strengthens the confidence on the estimated baryonic density of the Universe. However, there is an important discrepancy between the deduced 7Li abundance and the one observed in halo stars of our Galaxy, supposed, until now, to represent the primordial abundance of this isotope. The origin of this discrepancy, observational, nuclear or more fundamental remains to be clarified. The possible role of the up to now neglected 7Be(d,p)2\alpha and 7Be(d,\alpha)5Li reactions is considered. Comment: Invited contribution to the Origin of Matter and Evolution of the Galaxies (OMEG03) conference, RIKEN, Japan. Proceedings to appear in World Scientific
[show abstract][hide abstract] ABSTRACT: The stopping powers of C, CH2, Al, Ni, and polyvynilchloride (PVC) for several light ions (9Be,11B,12C,14N,16O,19F,20Ne) with an incident energy of 1 MeV/amu have been measured at the Louvain-la-Neuve cyclotron facility. Stopping powers are given relative to the one for 5.5 MeV 4He ions with an uncertainty of less than 1%. We compare our results with two widely used semiempirical models and we discuss some implications in nuclear astrophysics studies.
[show abstract][hide abstract] ABSTRACT: Mecanografiado Tesis (Lic. en Educación), Universidad de los Andes, Facultad de Humanidades y Educación, Escuela de Educación, Mención Preescolar, Mérida, 1990 Incluye bibliografía e indice